Composite materials have been widely used in a variety of applications. Typical composite materials are based on a matrix in the form of a glass fiber preform such as glass cloth, glass tape, glass mat and glass paper or a mica preform which is bound with a resin binder such as epoxy, phenol, polyimide and polyamide resins. Among these, those composite materials having a matrix bound with an epoxy or polyimide resin are often used as printed circuit board laminates which are required to have high heat resistance because the laminates are dipped in a molten solder bath in a wiring step. With the recent advance of the technology, printed circuit board laminates are required to be thinner and more resistant to soldering heat.
One well-known prior art attempt for improving various properties of such laminates including mechanical strength, electrical properties, water and boiling water resistance, and chemical resistance is a pretreatment of a matrix with a silane coupling agent such as .gamma.-aminopropyltriethoxysilane, .beta.-aminoethyl-.gamma.-aminopropyltrimethoxysilane, and .gamma.-glycidoxy. propyltrimethoxysilane to improve bonding properties prior to treatment with a resin binder. The pretreatment with a silane coupling agent, however, cannot fully meet the requirement because substantial curing strains are induced at the interface between the silane coupling agent-treated matrix and the resin binder, which are undesirable for soldering heat resistance.
Some solutions to this problem are known in the art, for example, from Japanese Patent Publication No. 20609/1973 disclosing treatment with a hydrochloride of a silane compound of the formula: ##STR1## Japanese Patent Publication No. 41771/1982 disclosing treatment with an aniline-substituted silane compound, and Japanese Patent Application Kokai No. 48832/1989 disclosing treatment with a silane compound of the formula: ##STR2## wherein R.sup.5 is a methyl or ethyl group, R.sup.6 is a divalent hydrocarbon group having 1 to 6 carbon atoms, and n is an integer of 4 to 8. However, laminates pretreated with these compounds are less resistant against blistering in thin film form.
The printed circuit board laminates have the problem that when dipped in molten solder, differential stresses due to the difference in coefficient of thermal expansion between the matrix and the binder resin, and in some cases, between the composite material and a copper cladding bonded to the surface for circuit wiring can break the bond therebetween. Therefore, it is desired for these products to improve heat shock resistance as well as soldering heat resistance.